In recent years, for saving of resources, in place of paper recycle use of recycling used papers, to be suited to further saving of resources and environmental protection, an art for reusing papers has been developed. The paper reuse eliminates image information printed on a paper using a decolorization toner and repeatedly uses the same paper several times to ten times or so to output new image information. By doing this, the use amount of paper can be reduced greatly and energy conservation and resource saving can be realized. Therefore, by a method for stripping the decolorization toner mechanically or chemically after printing so as to repeatedly reuse a paper, the printed part can be eliminated. Or, by a method for reacting the decolorization toner with heat, light, or chemicals, the printed part can be eliminated. As mentioned above, the decolorization toner is different in the characteristic from ordinary toner.
Conventionally, as an apparatus for forming images using such a decolorization toner, for example, as disclosed in Japanese Patent Application Publication No. 6-95494, there is an image forming apparatus available for executing both image forming by an ordinary toner and image forming by a decolorization toner.
The image forming apparatus disclosed in Japanese Patent Application Publication No. 6-95494 is equipped with both a developing device for developing by an ordinary toner which can retain printed images in the image forming apparatus for a long period of time and a developing device for developing by a decolorization toner, selects either of the developing devices, and forms images under the process condition according to the concerned toner.
However, the decolorization toner and ordinary toner are different in the toner characteristic from each other, so that between image forming by the decolorization toner and image forming by the ordinary toner, various process conditions for image forming are different. Furthermore, image forming by the decolorization toner, on the assumption of decolorization like a simple memo, does not always pursue image quality. As compared with it, the ordinary toner is used for official letters for long-term retention or submission to outside and is required for high image quality. As mentioned above, the decolorization toner and ordinary toner are different in the use object, thereby are different in the image output characteristic.
As mentioned above, although the decolorization toner and ordinary toner are different in use and characteristic from each other, as the image forming apparatus disclosed in Japanese Patent Application Publication No. 6-95494, when it is intended to obtain satisfactory image forming by both toners by the same image forming apparatus, the image forming process is different between the toners. Therefore, due to a difference between the number of times of image forming using the decolorization toner and the number of times of image forming using the ordinary toner, the life of various expendables is changed. Further, the adjustment of various process conditions for image quality maintenance is changed, so that appropriate life control of expendables and appropriate adjustment of the image process conditions cannot be realized and a problem arises that the image quality is lowered.